Brake pads, I need them for riding buddies as often as I need them for myself.
Multi tool with chain splitter, power link(s)
Tubeless worm kit with some fat worms
tubes and a decent sized pump
Random sweets of indeterminate age

Whats a chain ring tool? The thing that holds the nuts on the back of the chain ring? You also mentioned cleat bolts...am I right in thinking the granny ring bolts will fit a cleat?

mikewsmith - why not carry Powerlinks? They are the tiniest item in my tool kit. Why try and bodge a chain back together when you could carry a permanent fix?

I carry a hypercracker lock ring remover (although with swoopy modern frames its not always the easiest to use) but seeing as no one else will have a chance of removing a chain thats deep behind a cassette I keep it just in case. It presumably fits centrelock discs too.

mikewsmith - why not carry Powerlinks? They are the tiniest item in my tool kit. Why try and bodge a chain back together when you could carry a permanent fix?

Because a well fixed chain is a permanent fix, powerlinks are tiny and prone to getting lost in bags in my experience, having never really struggled with chain tools It take only slightly more effort to fix it without a powerlink.

I carry a hypercracker lock ring remover (although with swoopy modern frames its not always the easiest to use) but seeing as no one else will have a chance of removing a chain thats deep behind a cassette I keep it just in case. It presumably fits centrelock discs too.

Topeak hexus
2 proper tyre levers
chainlink
Almost worn out brake pads (because they're easier to fit trailside than new ones
Couple of cable ties
A couple of bolts (seriously, you wouldn't believe how useful this is)
Toothpaste tube tyre boot
Mechhanger. Though obviously, a mechhanger for a bike I no longer own, not the bike I'm actually riding.